1. Field of the Invention
The invention generally relates to a software development platform, and more particularly, a software development platform for providing a universal unifying interface to a plurality of programmable logic controllers.
2. Background Description
Programmable Logic Controllers (PLCs) typically include a customized piece of hardware that has an instruction set geared for the industrial control industry. This piece of hardware is often referred to as a Hard PLC. The programming language is usually ladder logic or some other language that is appropriate for the control application The programs (control programs) usually involve the manipulation of memory areas in the PLC that are tied through other specific pieces of hardware (I/O modules) to machinery such as, for example, switches, pumps, motors, machines, etc. These I/O modules are usually mounted on a rack and can be accessed over a network.
In recent years, the control industry has expanded to take advantage of the power of the Personal Computer (PC). A Soft PLC is a software version of the Hard PLC. Instead of having actual circuitry boards that execute the control program, a software program that runs on the PC executes the program. Additional cards may be inserted into the PC chassis to allow for access to the I/O modules. The Soft PLC will interface with these cards which, in turn, interface with the I/O modules.
There is another version of the PLC called a Slot PLC. This is a piece of hardware that is in the form of a card that can be inserted into a PC's chassis. The Slot PC contains substantial portions of hard PLC circuitry (or similar) and behaves substantially like a Hard PLC, but has a limited amount of accessibility and interaction to any other applications on the PC. Essentially, it is a Hard PLC on a PC card form with limited interaction with software running on the PC itself.
However, developing applications software for each of these types of PLCs can be exceedingly costly since the interfaces between PC applications and each type of PLC are different and the programming methodology within each type of PLC may be substantially different. Providing enhancements to these different types of PLCs, so that they are evolved with the same or similar features, is difficult and expensive. Design and development time, cost, and reliability issues to replicate functionality for each of these PLC types are an impediment to efficient and cost-effective life-cycle product development.